KR102552298B1 - Display device and driving method thereof - Google Patents

Abstract

The present invention relates to a display device capable of improving image quality.
In the display device driven by being divided into a driving period for displaying an image and a sensing period for sensing characteristic information of a driving transistor included in each pixel according to an embodiment of the present invention; pixels positioned to be connected to scan lines and data lines; a scan driver for supplying a scan signal to the scan lines; a data driver for supplying at least one of a reference voltage and a data signal to the data lines; a sensing unit connected to sensing lines formed parallel to the data lines and configured to sense the characteristic information via the sensing lines during the sensing period; control lines formed parallel to the scan lines; a first switch connected between the ith (i is a natural number) scan line and the ith control line; A second switch is connected between the ith control line and the i+1th scan line and does not overlap a turn-on period with the first switch.

Description

Display device and its driving method {DISPLAY DEVICE AND DRIVING METHOD THEREOF}

Embodiments of the present invention relate to a display device and a driving method thereof, and more particularly, to a display device capable of improving image quality and a driving method thereof.

As information technology develops, the importance of a display device as a connection medium between a user and information is being highlighted. In response to this, the use of display devices such as liquid crystal display devices and organic light emitting display devices is increasing.

Among display devices, an organic light emitting display device displays an image using pixels connected to a plurality of scan lines and data lines. To this end, each of the pixels includes an organic light emitting diode and a driving transistor.

The driving transistor controls the amount of current supplied to the organic light emitting diode in response to the data signal supplied from the data line. The organic light emitting diode generates light with a predetermined luminance in response to the amount of current supplied from the driving transistor.

In order for a display device to display an image of uniform quality, a driving transistor included in each of the pixels must supply a uniform current to the organic light emitting diode in response to a data signal. However, a driving transistor included in each of the pixels has a unique characteristic value that may vary.

For example, the threshold voltage and mobility of the driving transistor may be set differently in each pixel, and thus image quality may deteriorate.

Accordingly, the present invention relates to a display device capable of improving image quality by compensating for variation in characteristics of a driving transistor and a method for driving the same.

In the display device driven by being divided into a driving period for displaying an image and a sensing period for sensing characteristic information of a driving transistor included in each pixel according to an embodiment of the present invention; pixels positioned to be connected to scan lines, data lines, sensing lines, and control lines; a scan driver for supplying a scan signal to the scan lines; a data driver for supplying at least one of a reference voltage and a data signal to the data lines; a sensing unit configured to sense the characteristic information via the sensing lines during the sensing period; the control lines formed parallel to the scan lines; a first switch connected between the ith (i is a natural number) scan line and the ith control line; a second switch connected between the i-th control line and the i+1-th scan line, and not overlapping a turn-on period with the first switch; When the first switch is turned on, the ith control line receives a scan signal from the ith scan line, and when the second switch is turned on, the ith control line receives a scan signal from the i+1th scan line. is supplied with

According to an embodiment, the reference voltage is set to a voltage through which current flows in the driving transistor.

According to an embodiment, the first switch is turned on during the driving period.

According to an embodiment, the scan driver sequentially supplies scan signals to the scan lines during the driving period.

According to an embodiment, the scan signal supplied to the i+1 th scan line partially overlaps the scan signal supplied to the i th scan line.

According to an embodiment, the sensing period is set to a first sensing period in which mobility information of the driving transistor is sensed and a second sensing period in which threshold voltage information of the driving transistor is sensed.

According to an embodiment, the second switch is turned on during the first sensing period.

According to an embodiment, the scan driver sequentially supplies scan signals to the scan lines during the driving period.

According to the embodiment, the scan signal supplied to the i th scan line and the scan signal supplied to the i th control line partially overlap each other.

According to an embodiment, the data driver sequentially supplies a black grayscale data signal and the reference voltage to the data lines during the partial period.

According to an embodiment, the first switch is turned on during the second sensing period.

According to an embodiment, during the second sensing period, the scan driver sequentially supplies scan signals to the scan lines, and the scan signals do not overlap each other.

According to an embodiment, the data driver supplies the reference voltage to the data lines during a partial period during which the scan signal is supplied.

According to an embodiment, the sensing unit includes third switches each formed between an initialization power source and the sensing lines; an analog-to-digital converter connected to at least one sensing line and converting a voltage applied to the sensing lines into digital sensing data in response to the characteristic information of the driving transistor; A compensation unit including a memory for storing the sensing data is provided.

According to an embodiment, the third switches are set to a turn-on state during the driving period, and turn-on and turn-off are repeated during the sensing period.

According to an embodiment, the sensing unit is positioned between each of the sensing lines and the analog-to-digital converter, and further includes fourth switches whose turn-on periods do not overlap with the third switches.

According to an embodiment, each of the pixels positioned on the i-th horizontal line includes an organic light emitting diode; the driving transistor for controlling an amount of current flowing from a first driving power source to a second driving power source via the organic light emitting diode in response to a voltage of a first node; a second transistor connected between the first node and a data line, and having a gate electrode connected to the i-th scan line; a third transistor connected between the second electrode of the driving transistor and a sensing line, and having a gate electrode connected to the i-th control line; A storage capacitor is connected between the first node and a second electrode of the driving transistor.

According to an embodiment, a timing control unit for generating second data using first data supplied from the outside in correspondence with the characteristic information is further included.

A driving period for displaying an image according to an embodiment of the present invention, a first sensing period for sensing mobility information of a driving transistor included in each pixel, and a second sensing period for sensing threshold voltage information of the driving transistor A method of driving a display device driven by divided periods includes turning on a second transistor connected between a gate electrode of the driving transistor and a data line during the first sensing period; and then turning on a third transistor connected between the second electrode of the driving transistor and the sensing line, and sequentially applying a black gradation data signal and a reference voltage through which current can flow in the driving transistor to the data line. Supplying, turning off the second transistor, and sensing a voltage applied to the sensing line as the mobility information while maintaining a turn-on state of the third transistor.

According to an embodiment, simultaneously turning on the second transistor and the third transistor during the second sensing period, initializing the sensing line to a voltage of an initialization power supply, and applying the reference voltage to the data line. and sensing a voltage applied to the sensing line as the threshold voltage information.

According to the display device and its driving method according to an embodiment of the present invention, threshold voltage and mobility information of a driving transistor included in each pixel may be sensed. Then, corresponding to the threshold voltage and mobility information, bits of the first data input from the outside are changed to generate second data, and a data signal is generated using the second data. In this case, light of uniform luminance is emitted from each of the pixels in response to the data signal regardless of the threshold voltage and mobility deviation of the driving transistor, thereby improving image quality.

1 is a diagram illustrating a display device according to an exemplary embodiment of the present invention.
2A and 2B are diagrams illustrating an embodiment of a pixel shown in FIG. 1 .
3A and 3B are diagrams illustrating an embodiment of a channel included in the sensing unit of FIG. 1 .
4 is a diagram showing an embodiment of a driving waveform supplied during a driving period.
5 is a diagram illustrating an example of a driving waveform supplied during a first sensing period.
FIG. 6 is a diagram showing the driving waveform of FIG. 5 in detail.
FIG. 7 is a diagram illustrating mobility sensing voltages corresponding to whether the second and third transistors shown in FIG. 2A are turned on.
8 is a diagram illustrating an example of a driving waveform supplied during a second sensing period.

Hereinafter, with reference to the accompanying drawings, embodiments of the present invention and other matters necessary for those skilled in the art to easily understand the contents of the present invention will be described in detail. However, since the present invention can be implemented in many different forms within the scope described in the claims, the embodiments described below are merely illustrative regardless of whether they are expressed or not.

That is, the present invention is not limited to the embodiments disclosed below, but can be implemented in various different forms, and in the following description, when a part is connected to another part, it is directly connected. In addition, it includes the case where it is electrically connected with another element interposed therebetween. In addition, it should be noted that the same reference numerals and symbols refer to the same components in the drawings, even if they are displayed on different drawings.

1 is a diagram illustrating a display device according to an exemplary embodiment of the present invention. In FIG. 1 , an embodiment of the present invention will be described on the assumption that the display device is an organic light emitting display device for convenience of description, but the display device of the present invention is not limited to the organic light emitting display device.

Referring to FIG. 1 , a display device according to an exemplary embodiment includes a scan driver 100 , a data driver 200 , a pixel unit 300 , a sensing unit 400 and a timing controller 500 .

A display device according to an embodiment of the present invention may be driven by dividing into a sensing period and a driving period. The sensing period is set as a period for extracting deviation information of the driving transistor included in each of the pixels 310 . To this end, the sensing period includes a first sensing period for extracting mobility information of a driving transistor included in each of the pixels 310 and a first sensing period for extracting threshold voltage information of a driving transistor included in each of the pixels 310. It can be driven by dividing it into two sensing periods. The driving period is set as a period for displaying a predetermined image in response to a data signal.

The scan driver 100 supplies scan signals to the scan lines S1 to Sn+1 in response to the control of the timing controller 500 . For example, the scan driver 100 may sequentially supply scan signals to the scan lines S1 to Sn+1. When scan signals are sequentially supplied to the scan lines S1 to Sn+1, the pixels 310 are selected in units of horizontal lines. To this end, the scan signal is set to a gate-on voltage at which the transistors included in the pixels 310 can be turned on.

Additionally, the scan driver 100 may supply a scan signal to the i+1th scan line (Si+1) such that it partially overlaps with the scan signal supplied to the i (i is a natural number) scan line (Si). Also, the scan driver 100 may supply the scan signal to the i+1th scan line Si+1 so as not to overlap with the scan signal supplied to the ith scan line Si.

For example, the scan driver 100 may supply a scan signal to the i+1th scan line Si+1 so as to partially overlap with the scan signal supplied to the ith scan line Si during the driving period and the first sensing period. . Also, the scan driver 100 may supply the scan signal to the i+1th scan line Si+1 so as not to overlap with the scan signal supplied to the ith scan line Si during the second sensing period.

The data driver 200 supplies a reference voltage and/or a data signal to the data lines D1 to Dm in response to the control of the timing controller 500 .

The data driver 200 receives the second data Data2 from the timing controller 500 during the driving period and generates a data signal corresponding to the supplied second data Data2. The data driver 200 that generates the data signal supplies the data signal to the data lines D1 to Dm. Data signals supplied to the data lines D1 to Dm are supplied to the pixels 310 selected by the scan signal. Then, the pixels 310 emit light having a luminance corresponding to the data signal during the driving period, and accordingly, a predetermined image is displayed in the pixel unit 300 .

The data driver 200 repeatedly supplies a first grayscale data signal and a reference voltage to the data lines D1 to Dm during the first sensing period. For example, the data driver 200 may sequentially supply the first grayscale data signal, the reference voltage, the first grayscale data signal, and the reference voltage to the data lines D1 to Dm while the scan signal is supplied. Here, the first gradation may be set to a data signal of black gradation. Also, the reference voltage may be set to a predetermined voltage through which a current may flow in a driving transistor included in each of the pixels 310 .

The data driver 200 supplies a reference voltage to the data lines D1 to Dm during the second sensing period. For example, the data driver 200 may supply the reference voltage to the data lines D1 to Dm during at least a portion of the period during which the scan signal is supplied.

Meanwhile, the above-described second data Data2 is a value based on the first data Data1 input from the outside corresponding to an image to be displayed on the pixel unit 300, and is particularly driven by each of the pixels 310. It can be set to a value obtained by changing the first data Data1 so that the deviation of the transistor can be compensated for.

The sensing unit 400 is connected to sensing lines SEN1 to SENm positioned parallel to the data lines D1 to Dm. The sensing unit 400 senses characteristic information of a driving transistor included in each of the pixels 310 during a sensing period in response to the control of the timing controller 500 . For example, the sensing unit 400 senses mobility information of the driving transistor included in each of the pixels 310 during the first sensing period, and the threshold of the driving transistor included in each of the pixels 310 during the second sensing period. Voltage information may be sensed.

The control lines CL1 to CLn are disposed parallel to the scan lines S1 to Sn+1. These control lines CL1 to CLn are electrically connected to one of the scan lines S1 to Sn+1. To this end, the display device includes a plurality of first switches SW1 and second switches SW2.

The first switch (SW1) is located between the scan line and the control line located on the same horizontal line. For example, the first switch SW1 is positioned between the i th scan line Si and the i th control line CLi. In this case, when the first switch SW1 is turned on, the i th scan line Si and the i th control line CLi are electrically connected. Accordingly, when the first switch SW1 is turned on, the i th control line CLi receives a scan signal from the i th scan line Si.

The second switch SW2 is located between the control line located on the current horizontal line and the scan line located on the next horizontal line. For example, the second switch SW2 is positioned between the ith control line CLi and the i+1th scan line Si+1. In this case, when the second switch SW2 is turned on, the ith control line CLi and the i+1th scan line Si+1 are electrically connected. Accordingly, when the second switch SW2 is turned on, the ith control line CLi receives a scan signal from the i+1th scan line Si+1. Turn-on times of the first switch SW1 and the second switch SW2 do not overlap. A detailed description of the operation process of the first switch SW1 and the second switch SW2 will be described later in connection with driving waveforms.

The pixel unit 300 includes pixels 310 disposed to be connected to a plurality of scan lines S1 to Sn, control lines CL1 to CLn, sensing lines SEN1 to SENm, and data lines D1 to Dm. provide In this case, the pixel unit 300 may be set as a display area for displaying a predetermined image. Each of the pixels 310 is electrically connected to the first driving power source ELVDD and the second driving power source ELVSS. Here, the first driving power source ELVDD may be set to a higher voltage than the second driving power source ELVSS.

Each of the pixels 310 includes a driving transistor and an organic light emitting diode. The driving transistor controls the amount of current flowing from the first driving power source ELVDD to the second driving power source ELVSS via the organic light emitting diode in response to the data signal. At this time, the organic light emitting diode emits light with a luminance corresponding to the amount of current supplied from the driving transistor. However, when a data signal corresponding to a black gradation is supplied, the driving transistor controls current not to flow through the organic light emitting diode, and accordingly, the organic light emitting diode is set to a non-emitting state.

The timing controller 500 controls the scan driver 100 , the data driver 200 and the sensing unit 400 . Also, the timing controller 500 may generate second data Data2 by changing bits of the first data Data1 in response to the deviation information of the driving transistor sensed by the sensing unit 400 .

Meanwhile, in FIG. 1, only components necessary for explaining the present invention are shown, and various components may be added to an actual display device. For example, one or more dummy scan lines may be additionally included for driving stability. In addition, the scan driver 100 , the data driver 200 , the sensing unit 400 , and/or the timing controller 500 may be mounted on a panel (not shown) together with the pixel unit 300 . Similarly, the first switches SW1 and the second switches SW1 may also be mounted on the panel or located outside the panel.

FIG. 2A is a diagram illustrating an embodiment of a pixel shown in FIG. 1 . In FIG. 2A, for convenience of explanation, a pixel connected to the mth data line Dm and the nth scan line Sn is illustrated.

Referring to FIG. 2A , a pixel 310 according to an embodiment of the present invention includes an organic light emitting diode (OLED) and a pixel circuit 312 .

The anode electrode of the organic light emitting diode OLED is connected to the pixel circuit 312, and the cathode electrode is connected to the second driving power source ELVSS. Such an organic light emitting diode (OLED) emits light with a luminance corresponding to the amount of current supplied from the pixel circuit 312 .

The pixel circuit 312 controls the amount of current flowing from the first driving power source ELVDD to the second driving power source ELVSS via the organic light emitting diode OLED in response to the data signal. To this end, the pixel circuit 312 includes a first transistor (M1: driving transistor), a second transistor (M2), a third transistor (M3), and a storage capacitor (Cst).

Here, at least one of the first to third transistors M1 to M3 may be an oxide semiconductor thin film transistor including an active layer made of an oxide semiconductor. Also, at least one of the first to third transistors M1 to M3 may be an LTPS thin film transistor including an active layer made of polysilicon.

The first electrode of the first transistor M1 is connected to the first driving power source ELVDD, and the second electrode is connected to the anode electrode of the organic light emitting diode OLED. Also, the gate electrode of the first transistor M1 is connected to the first node N1. The first transistor M1 controls the amount of current flowing from the first driving power source ELVDD to the second driving power source ELVSS via the organic light emitting diode OLED in response to the voltage of the first node N1. .

The first electrode of the second transistor M2 is connected to the data line Dm, and the second electrode is connected to the first node N1. And, the gate electrode of the second transistor M2 is connected to the scan line Sn. The second transistor M2 is turned on when a scan signal is supplied to the scan line Sn to electrically connect the data line Dm and the first node N1.

The first electrode of the third transistor M3 is connected to the second electrode of the first transistor M1, and the second electrode is connected to the sensing line SENm. And, the gate electrode of the third transistor M3 is connected to the control line CLn. The third transistor M3 is turned on when a scan signal is supplied to the control line CLn, and electrically connects the sensing line SENm and the second electrode of the first transistor M1.

The storage capacitor Cst is connected between the first node N1 and the second electrode of the first transistor M1. The storage capacitor Cst stores the voltage of the first node N1.

Meanwhile, in the embodiment of the present invention, the circuit structure of the pixel 310 is not limited by FIG. 2A. For example, in an embodiment of the present invention, the organic light emitting diode OLED may be positioned between the first driving power source ELVDD and the first electrode of the first transistor M1 as shown in FIG. 2B. That is, in an embodiment of the present invention, the circuit structure of the pixel 310 may be variously changed to include a third transistor M3 for sensing the characteristic information of the first transistor M1.

The luminance of the pixel 310 described above is mainly determined by the data signal. However, the characteristic value of the first transistor M1 may be additionally reflected in the luminance of the pixel 310 . That is, in the embodiment of the present invention, an external compensation method is applied in which the characteristic information of the first transistor M1 is sensed during the sensing period and the first data Data1 is changed by reflecting the sensed characteristic information. In this case, an image of a uniform quality can be displayed in the pixel unit 300 regardless of the variation in the characteristics of the first transistor M1.

According to an embodiment, the sensing period for sensing the characteristic information of the first transistor M1 included in each of the pixels 310 may be performed at least once before shipment of the display device. In this case, the initial characteristic information of the first transistors M1 is stored before shipment of the display device, and the first data Data1 is corrected (ie, the second data Data2 is generated) using the characteristic information, thereby generating the pixel unit. In 300, an image of uniform quality can be displayed.

Also, the sensing period may be performed at predetermined time intervals even after actual use of the display device. For example, the sensing period may be disposed at a part of the time when the display device is turned on and/or turned off at every predetermined time. Then, even if the characteristics of the driving transistor included in each of the pixels 310 change in response to the amount of usage, the characteristic information can be updated in real time and reflected in the generation of the data signal. Therefore, the pixel unit 300 can continuously display images of uniform quality.

FIG. 3A is a diagram illustrating an embodiment of a channel included in the sensing unit of FIG. 1 . In FIG. 3A, only one channel of the sensing unit connected to the pixel of FIG. 2A is illustrated. However, a plurality of channels connected to each of the sensing lines SEN1 to SENm may be provided inside the sensing unit. Also, the analog digital converter 410 shown in FIG. 3A (hereinafter referred to as "ADC") and the compensator 420 may share a plurality of channels.

Referring to FIG. 3A , the sensing unit 400 of the present invention includes a third switch SW3 connected to an initialization power supply Vint, an ADC 410 and a compensation unit 420.

The third switch SW3 is connected between the sensing line SENm and the initialization power supply Vint. The third switch SW3 is turned on or off in response to the control of the timing controller 500 . When the third switch SW3 is turned on, the voltage of the initialization power source Vint is supplied to the sensing line SENm. Here, the initialization power source Vint is set as a constant voltage source and is used to initialize the sensing line SENm.

The ADC 410 converts the voltage of the sensing line SENm into digital sensing data. For example, during the sensing period, a predetermined voltage is applied to the sensing line SENm in response to the variation in the characteristics of the first transistor M1, and the ADC 410 converts the predetermined voltage into digital sensing data, thereby compensating the sensing line SENm. (420).

The compensator 420 stores the sensing data from the ADC 410. To this end, a memory not shown may be additionally provided in the compensation unit 420 . Such compensating unit 420 may additionally include various currently known components and may be included inside the timing controller 500 .

Meanwhile, in the present invention, the sensing unit 400 may further include a fourth switch SW4 positioned between the sensing line SENm and the ADC 410 as shown in FIG. 3B. The fourth switch SW4 may be turned on or off alternately with the third switch SW3.

For example, the fourth switch SW4 may maintain a turned-off state during a period in which the third switch SW3 is turned on and the voltage of the initialization power source Vint is supplied to the sensing line SENm. In this case, it is possible to improve driving stability by preventing unnecessary voltage from being supplied to the ADC 410 .

Additionally, CLine shown in FIGS. 3A and 3B indicates a line capacitor CLine equivalently formed to the sensing line SENm. The line capacitor CLine stores the voltage applied to the sensing line SENm.

4 is a diagram showing an embodiment of a driving waveform supplied during a driving period.

Referring to FIG. 4 , during the driving period, the first switches SW1 are turned on and the second switches SW2 are turned off. When the first switches SW1 are turned on, the i th control line CLi is electrically connected to the i th scan line Si. Also, during the driving period, the third switches SW3 are set to a turn-on state. When the third switches SW3 are turned on, the voltage of the initialization power source Vint is supplied to the sensing lines SEN1 to SENm.

During the driving period, the scan driver 100 sequentially supplies scan signals to the scan lines S1 to Sn+1. At this time, the scan driver 100 supplies a scan signal to the i+1th scan line Si+1 so as to overlap with the scan signal supplied to the ith scan line Si for a partial period. For example, when the scan signal is set to a period of 2H, the scan driver 100 uses the i+1th scan line Si+1 to overlap the scan signal supplied to the ith scan line Si for a period of 1H. can supply

The scan signals supplied to the scan lines S1 to Sn+1 are also supplied to the control lines CL1 to CLn electrically connected to the scan lines S1 to Sn+1. For example, the scan signal supplied to the i th scan line Si is supplied to the i th control line CLi.

Therefore, the scan signal supplied to the nth scan line Sn is also supplied to the nth control line CLn. When a scan signal is supplied to the nth scan line Sn, the second transistor M2 is turned on, and when a scan signal is supplied to the nth control line CLn, the third transistor M3 is turned on.

When the second transistor M2 is turned on, the data line Dm and the first node N1 are electrically connected. When the third transistor M3 is turned on, the sensing line SENm and the second electrode of the first transistor M1 are electrically connected.

While the second transistor M2 is turned on, the n−1 th data signal DSn−1 and the n th data signal DSn are sequentially supplied to the data line Dm. Here, the n−1 th data signal DSn−1 denotes a data signal corresponding to the n−1 th horizontal line, and the n−1 th data signal DSn denotes a data signal corresponding to the nth horizontal line.

The n−1 th data signal DSn−1 and the n th data signal DSn sequentially supplied to the data line Dm are supplied to the first node N1 via the second transistor M2. At this time, the storage capacitor Cst stores a voltage corresponding to the finally supplied nth data signal DSn.

When the third transistor M3 is turned on, the voltage of the initialization power source Vint from the sensing line SENm is supplied to the second electrode of the first transistor M1. Then, the nth data signal DSn is supplied to one terminal of the storage capacitor Cst, and the voltage of the initialization power source Vint is stored to the other terminal. In this case, the storage capacitor Cst stores a voltage corresponding to a difference voltage between the nth data signal DSn and the initialization power supply Vint.

Here, since the initialization power source Vint is set to a constant voltage, the voltage stored in the storage capacitor Cst is determined by the nth data signal DSn.

Meanwhile, in an embodiment of the present invention, the voltage of the initialization power supply (Vint) is supplied to the other terminal of the storage capacitor (Cst) while the voltage of the data signal is being charged in the storage capacitor (Cst), and accordingly, a desired voltage is stored. can

In detail, the other terminal of the storage capacitor Cst is electrically connected to the anode electrode of the organic light emitting diode OLED. Here, the anode electrode voltage of the organic light emitting diode (OLED) may be changed in response to deterioration of the organic light emitting diode (OLED).

In this case, the voltage applied to the anode electrode of the organic light emitting diode (OLED) may be set differently for each pixel 310 . Then, even if the same data signal is supplied, the voltage charged in the storage capacitor Cst in each of the pixels 310 may be set differently. On the other hand, if the voltage of the initialization power source Vint is supplied to the other terminal of the storage capacitor Cst during the period in which the voltage is charged in the storage capacitor Cst, as in the present invention, regardless of the deterioration of the organic light emitting diode OLED. A desired voltage may be charged in the storage capacitor Cst.

After the voltage corresponding to the mth data signal DSm is charged in the storage capacitor Cst, the supply of the scan signal to the nth scan line Sn and the nth control line CLn is stopped. When the supply of scan signals to the nth scan line (Sn) and the nth control line (CLn) is stopped, the second transistor (M2) and the third transistor (M3) are set to a turn-off state.

Thereafter, the first transistor M1 controls the amount of current supplied to the organic light emitting diode OLED in response to the voltage applied to the first node N1. Then, the organic light emitting diode OLED emits light with a luminance corresponding to the amount of current from the first transistor M1.

In the embodiment of the present invention, during the driving period, the pixel unit 300 displays a predetermined image while repeating the above-described process.

5 is a diagram illustrating an example of a driving waveform supplied during a first sensing period.

Referring to FIG. 5 , during the first sensing period, the first switches SW1 are turned off and the second switches SW2 are turned on. When the second switches SW2 are set to a turn-on state, the ith control line CLi is electrically connected to the i+1th scan line Si+1. Also, during the first sensing period, the third switches SW3 repeat turn-on and turn-off. When the third switches SW3 are turned on, the voltage of the initialization power source Vint is supplied to the sensing lines SEN1 to SENm.

During the first sensing period, the scan driver 100 sequentially supplies scan signals to the scan lines S1 to Sn+1. At this time, the scan driver 100 supplies a scan signal to the i+1th scan line Si+1 so as to overlap with the scan signal supplied to the ith scan line Si for a partial period.

The scan signals supplied to the scan lines S1 to Sn+1 are also supplied to the control lines CL1 to CLn electrically connected to the scan lines S1 to Sn+1. For example, the scan signal supplied to the i+1th scan line Si+1 is supplied to the ith control line CLi.

Therefore, the scan signal supplied to the n+1th scan line (Sn+1) is supplied to the nth control line (CLn).

The operation process will be described in detail in connection with FIGS. 3A, 5, and 6. First, a scan signal is supplied to the nth scan line Sn, and the second transistor M2 is turned on. When the second transistor M2 is turned on, the data line Dm and the first node N1 are electrically connected.

Thereafter, a scan signal is supplied to the nth control line CLn to overlap with the scan signal supplied to the nth scan line Sn for a partial period. Here, the scan signal supplied to the nth control line CLn is supplied from the n+1th scan line Sn+1.

Hereinafter, for convenience of explanation, the period during which the scan signal is supplied to the nth control line CLn will be described by dividing it into a first period T1 to a fourth period T4 as shown in FIG. 6 .

When a scan signal is supplied to the nth control line CLn, the third transistor M3 is turned on. When the third transistor M3 is turned on, the sensing line SENm and the second electrode of the first transistor M1 are electrically connected.

During the first period T1, the black data signal DS(B) is supplied to the data line Dm. When the black data signal DS(B) is supplied to the data line Dm, the first transistor M1 is turned off. At this time, a predetermined voltage corresponding to the mobility of the first transistor M1 included in the pixel 310 located on the n-1th horizontal line is applied to the sensing line SENm. The ADC 410 converts the voltage applied to the sensing line SENm into digital sensing data and supplies it to the compensating unit 420, and the compensating unit 420 stores the supplied sensing data.

In the second period T2, the reference voltage Vref is supplied to the data line Dm. The reference voltage Vref supplied to the data line Dm is supplied to the first node N1 of the pixel 310 located on the nth horizontal line. Here, the reference voltage (Vref) is set to a voltage at which the first transistor (M1) can be turned on, and accordingly, a current corresponding to the reference voltage (Vref) from the first transistor (M1) flows through the third transistor (M3). is supplied to the sensing line SENm via

During the second period T2, the third switch SW3 is set to a turn-on state. When the third switch SW3 is set to a turn-on state, the voltage of the initialization power source Vint is supplied to the sensing line SENm. That is, during the second period T2, the sensing line SENm is initialized with the voltage of the initialization power supply Vint. Therefore, during the second period T2, the sensing line SENm maintains the voltage of the initialization power source Vint regardless of the current flowing from the first transistor M1.

In the third period T3, the supply of scan signals to the nth scan line Sn is stopped. When the supply of the scan signal to the nth scan line Sn is stopped, the second transistor M2 is turned off. Therefore, the black data signal DS(B) supplied to the data line Dm during the third period T3 is not supplied to the first node N1.

Also, in the third period T3, the third switch SW3 is turned off. When the third switch SW3 is turned off, the voltage of the initialization power source Vint is not supplied to the sensing line SENm. Accordingly, a predetermined voltage corresponding to the current supplied from the pixel 310 located on the nth horizontal line is applied to the sensing line SENm during the third period T3.

Here, the voltage applied to the sensing line SENm is determined corresponding to the mobility of the first transistor M1. That is, voltages applied to the sensing lines SEN1 to SENm during the third period T3 may be differently set to correspond to the mobility of the driving transistor included in each of the pixels 310 .

The ADC 410 converts the voltage applied to the sensing line SENm into digital sensing data and supplies it to the compensating unit 420, and the compensating unit 420 stores the supplied sensing data. At this time, the sensing data stored in the compensation unit 420 corresponds to mobility information of the driving transistor included in the pixel 310 connected to the mth data line Dm and the nth scan line Sn.

Meanwhile, in the embodiment of the present invention, during the third period T3, the second transistor M2 is turned off and the third transistor M3 is turned on. Then, one terminal (ie, the first node) of the storage capacitor Cst is set to a floating state.

Therefore, even if the voltage of the other terminal of the storage capacitor Cst increases in response to the increase in the voltage of the sensing line SENm, the charged voltage of the storage capacitor Cst is maintained constant. That is, the Vgs voltage of the first transistor M1 is maintained constant during the third period T3, and accordingly, the accuracy of the mobility information of the first transistor M1 can be improved.

In other words, when one terminal of the storage capacitor Cst is not set to a floating state during the third period T3, the charging voltage of the storage capacitor Cst is changed in response to an increase in the voltage of the sensing line SENm. , and accordingly, the accuracy of the mobility information is lowered.

During the fourth period T4, the third switch SW3 is turned on and the voltage of the initialization power source Vint is supplied to the sensing line SENm. Then, the sensing line SENm is initialized with the voltage of the initialization power supply Vint.

In the embodiment of the present invention, mobility information of the driving transistor included in each of the pixels 310 is extracted while repeating the above-described process during the first sensing period.

FIG. 7 is a diagram illustrating mobility sensing voltages corresponding to whether the second and third transistors shown in FIG. 2A are turned on.

Referring to FIG. 7 , during a period in which a voltage corresponding to the mobility is applied to the sensing lines SEN1 to SENm (ie, the third period T3 in FIG. 6 ), the second transistor M2 and the third transistor M3 ) is set to the turn-on state, an accurate voltage corresponding to the mobility is not applied to the sensing lines SEN1 to SENm due to the voltage change of the storage capacitor Cst.

On the other hand, the second transistor M2 turns during the period in which the voltage corresponding to the mobility is applied to the sensing lines SEN1 to SENm, as in the embodiment of the present invention (ie, the third period T3 in FIG. 6). - When turned off and the third transistor M3 is set to a turn-on state, the voltage of the storage capacitor Cst does not change, so that an accurate voltage corresponding to the mobility is applied to the sensing lines SEN1 to SENm.

8 is a diagram illustrating an example of a driving waveform supplied during a second sensing period.

Referring to FIG. 8 , during the second sensing period, the first switches SW1 are turned on and the second switches SW2 are turned off. When the first switches SW1 are set to a turn-on state, the ith control line CLi is electrically connected to the ith scan line Si. The third switches SW3 are turned on during a part of the first part of the scan signal supply period. When the third switches SW3 are turned on, the voltage of the initialization power source Vint is supplied to the sensing lines SEN1 to SENm.

During the second sensing period, the scan driver 100 sequentially supplies scan signals to the scan lines S1 to Sn+1. At this time, the scan driver 100 supplies the scan signal to the i+1th scan line Si+1 so as not to overlap with the scan signal supplied to the ith scan line Si.

The scan signals supplied to the scan lines S1 to Sn+1 are also supplied to the control lines CL1 to CLn electrically connected to the scan lines S1 to Sn+1. For example, the scan signal supplied to the i th scan line Si is supplied to the i th control line CLi.

Therefore, the scan signal supplied to the nth scan line Sn is also supplied to the nth control line CLn. When a scan signal is supplied to the nth scan line Sn, the second transistor M2 is turned on, and when a scan signal is supplied to the nth control line CLn, the third transistor M3 is turned on.

When the second transistor M2 is turned on, the data line Dm and the first node N1 are electrically connected. When the third transistor M3 is turned on, the sensing line SENm and the second electrode of the first transistor M1 are electrically connected.

The third switch SW3 is turned on during the eleventh period T11 of the period in which the scan signal is supplied to the nth scan line Sn. When the third switch SW3 is turned on, the voltage of the initialization power source Vint is supplied to the sensing line SENm, and accordingly, the voltage of the sensing line SENm is initialized to the voltage of the initialization power source Vint.

The reference voltage Vref is supplied to the data line Dm during the twelfth period T12 of the period in which the scan signal is supplied to the nth scan line Sn. The reference voltage Vref supplied to the data line Dm is supplied to the first node N1. At this time, the first transistor M1 supplies a predetermined current to the sensing line SENm in response to the reference voltage Vref.

Then, the voltage of the sensing line SENm gradually rises. Finally, the voltage SENm of the sensing line rises to a voltage obtained by subtracting the threshold voltage of the first transistor M1 from the voltage of the reference power supply Vref. That is, the voltage applied to the sensing line SENm during the second sensing period is determined corresponding to the threshold voltage of the first transistor M1.

The ADC 410 converts the voltage applied to the sensing line SENm into digital sensing data and supplies it to the compensating unit 420, and the compensating unit 420 stores the supplied sensing data. At this time, the sensing data stored in the compensation unit 420 corresponds to threshold voltage information of a driving transistor included in the pixel 310 connected to the mth data line Dm and the nth scan line Sn.

Meanwhile, in an embodiment of the present invention, the width of the scan signal supplied during the second sensing period may be set to a sufficiently wide width so that a voltage corresponding to the threshold voltage of the first transistor M1 can be applied to the sensing line SENm. can

In the embodiment of the present invention, the threshold voltage information of the driving transistor included in each of the pixels 310 is extracted while repeating the above-described process during the second sensing period.

Although the technical idea of the present invention has been specifically described according to the above preferred embodiments, it should be noted that the above embodiments are for explanation and not for limitation. In addition, those skilled in the art will understand that various modifications are possible within the scope of the technical spirit of the present invention.

The scope of rights to the above-described invention is defined in the claims below, and is not bound by the description of the main body of the specification, and all modifications and changes falling within the scope of equivalents of the claims will fall within the scope of the present invention.

100: scan driver 200: data driver
300: pixel unit 310: pixel
312: pixel circuit 400: sensing unit
410: ADC 420: compensation unit
500: timing controller

Claims (20)

A display device driven by being divided into a driving period for displaying an image and a sensing period for sensing characteristic information of a driving transistor included in each pixel;
pixels positioned to be connected to scan lines, data lines, sensing lines, and control lines;
a scan driver for supplying a scan signal to the scan lines;
a data driver for supplying at least one of a reference voltage and a data signal to the data lines;
a sensing unit configured to sense the characteristic information via the sensing lines during the sensing period;
the control lines formed parallel to the scan lines;
a first switch connected between the ith (i is a natural number) scan line and the ith control line;
a second switch connected between the i-th control line and the i+1-th scan line, and not overlapping a turn-on period with the first switch;
When the first switch is turned on, the ith control line receives a scan signal from the ith scan line, and when the second switch is turned on, the ith control line receives a scan signal from the i+1th scan line. A display device characterized in that for receiving. According to claim 1,
The reference voltage is set to a voltage through which current flows in the driving transistor. According to claim 1,
The display device according to claim 1 , wherein the first switch is turned on during the driving period. According to claim 3,
The display device according to claim 1 , wherein the scan driver sequentially supplies scan signals to the scan lines during the driving period. According to claim 4,
The display device according to claim 1 , wherein the scan signal supplied to the i+1 scan line partially overlaps the scan signal supplied to the i th scan line. According to claim 1,
The sensing period is set to a first sensing period in which mobility information of the driving transistor is sensed and a second sensing period in which threshold voltage information of the driving transistor is sensed. According to claim 6,
The display device according to claim 1 , wherein the second switch is turned on during the first sensing period. According to claim 7,
The display device according to claim 1 , wherein the scan driver sequentially supplies scan signals to the scan lines during the driving period. According to claim 8,
The display device according to claim 1 , wherein a scan signal supplied to the i th scan line and a scan signal supplied to the i th control line overlap for a partial period. According to claim 9,
The display device according to claim 1 , wherein the data driver sequentially supplies a black grayscale data signal and the reference voltage to the data lines during the partial period. According to claim 6,
The display device according to claim 1 , wherein the first switch is turned on during the second sensing period. According to claim 11,
The display device according to claim 1 , wherein the scan driver sequentially supplies scan signals to the scan lines during the second sensing period, and the scan signals do not overlap each other. According to claim 12,
The display device according to claim 1 , wherein the data driver supplies the reference voltage to the data lines during a partial period during which the scan signal is supplied. According to claim 1,
the sensing unit
third switches each formed between an initialization power source and the sensing lines;
an analog-to-digital converter connected to at least one sensing line and converting a voltage applied to the sensing lines into digital sensing data in response to the characteristic information of the driving transistor;
A display device comprising a compensation unit including a memory for storing the sensing data. According to claim 14,
The third switches are
A display device characterized in that it is set to a turn-on state during the driving period, and turns-on and turn-off are repeated during the sensing period. According to claim 14,
the sensing unit
and fourth switches located between each of the sensing lines and the analog-to-digital converter, and not overlapping a turn-on period with the third switches. According to claim 1,
Each of the pixels located on the i-th horizontal line is
organic light emitting diodes;
the driving transistor for controlling an amount of current flowing from a first driving power source to a second driving power source via the organic light emitting diode in response to a voltage of a first node;
a second transistor connected between the first node and a data line, and having a gate electrode connected to the i-th scan line;
a third transistor connected between the second electrode of the driving transistor and a sensing line, and having a gate electrode connected to the i-th control line;
and a storage capacitor connected between the first node and a second electrode of the driving transistor. According to claim 1,
and a timing control unit for generating second data using first data supplied from the outside in correspondence with the characteristic information. A display device driven by being divided into a driving period for displaying an image, a first sensing period for sensing mobility information of a driving transistor included in each pixel, and a second sensing period for sensing threshold voltage information of the driving transistor In the driving method of
During the first sensing period
turning on a second transistor connected between a gate electrode of the driving transistor and a data line;
turning on a third transistor connected between a second electrode of the driving transistor and a sensing line after the second transistor is turned on;
sequentially supplying a black gradation data signal and a reference voltage through which current flows in the driving transistor to the data line;
turning off the second transistor;
and sensing a voltage applied to the sensing line as the mobility information while maintaining the turn-on state of the third transistor. According to claim 19,
During the second sensing period
turning on the second transistor and the third transistor at the same time;
Initializing the sensing line with a voltage of an initialization power supply;
supplying the reference voltage to the data line;
and sensing a voltage applied to the sensing line as the threshold voltage information.

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